Let raspberries thaw slightly at room temperature. Wash basil, shake dry. Pluck the leaves from the stalks and chop them finely, except for a little garnish. Wash lemon hot, grate dry and grate peel thinly.
Puree the raspberries and 80 g sugar with a hand blender. Stir in lemon zest and basil. Pour ice into a bowl and freeze for at least 4 hours.
Mix flour, cocoa powder and baking powder. Add 150 g sugar, rice drink and oil and mix to a smooth dough with the whisk of the hand mixer. Stir in nuts, except for 2 pieces, briefly. Pour the dough into an oiled and flour-spread square baking tin (17 x 17 cm).
Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 25 minutes. Take out and let cool in the form. Cut the cake into about 18 pieces. Chop the remaining nuts.
Form ice into balls. Arrange 1 piece of cake and 1 ball of ice cream. Sprinkle with nuts and decorate with basil. Use the rest of the cake for other purposes.